A drill chuck described in U.S. Pat. No. 5,765,839 has a body provided centered on an axis with an annular array of teeth and a plurality of jaws radially displaceable relative to the body between inner and outer positions. A tightening ring is axially fixed but rotatable about the axis on the body in a tightening direction and in an opposite loosening direction and a pair of screwthread formations between the tightening ring and the jaws move the jaws radially together on rotation of the tightening ring in the tightening direction and radially apart on rotation of the tightening ring in the loosening direction. A locking member engageable with the teeth and angularly fixed on the tightening ring is radially displaceable between a locking position engaging the teeth and preventing rotation of the ring in the loosening direction and a freeing position permitting free relative rotation of the body and the ring. A setting ring angularly displaceable on the tightening ring is formed with a pair of angularly spaced and radially open seats. A pair of angularly spaced abutments between the setting ring and the tightening ring limit angular movement of the sleeve on the ring. A cam on the setting ring is engageable with the locking member for displacing the locking member into the locking position when the setting ring is in one of its end positions and for displacing the locking member into the freeing position when the setting ring is in the other of its end positions.
Such a drill chuck has proven very satisfactory in practice, and consequently has been manufactured and marketed in very high volume. However, due to the presence of a locking device this drill chuck also has a relatively complex design that is costly to manufacture for use on a high-powered hammer drill.